1. Field of the Invention
The present invention relates to an automobile seat and a headrest thereof.
2. Description of the Related Art
Heretofore, a headrest has been provided on a seat back of an automobile seat to protect a user or an occupant seated in the seat in the event of a collision. As an example of the conventional headrest, there has been known a type capable of being moved upwardly and downwardly with respect to a seat back in a standing posture which is a normal usage position. This type of headrest can be moved downwardly with respect to the seat back so as to be set to a lower position (when the seat back is in the standing posture) in advance of an operation of rotating the seat back frontwardly to set the seat back to a frontwardly tilted posture. This makes it possible to prevent a problem, such as a situation where the headrest disturbs the operation of setting the seat back to the frontwardly tilted posture.
However, in this case, even when a user leans on the seat back in the standing posture during traveling of the automobile, the headrest is likely to be used under a condition that it is still set in the lower position after being moved downwardly with respect to the seat back. If the headrest is used in the lower position, it cannot fulfill its original protective function.
As means for solving this problem, there has been known a technique proposed, for example, in JP 11-180197A. In this technique, an automobile seat comprises a lock device and a restriction device. The lock device is adapted to selectively lock a standing posture of a seat back and release the locked state. The restriction device is adapted, when the seat back is locked in the standing posture by the lock device, to inhibit a headrest from being moved downwardly to a position equal to or lower than a given position, and, when the headrest is in a position equal to or lower than the given position, to inhibit the lock device from locking the standing posture of the seat back.
However, as in the technique disclosed in JP 11-180197A, if a downward movement of the headrest is constantly inhibited by the restriction device when the seat back is in the standing posture, the headrest cannot be moved downwardly as long as the seat back is in the standing posture, for example, even in a situation where a user wants to move the headrest downwardly during stopping of the automobile. Thus, the user is obliged to perform an operation of moving the headrest downwardly after setting the seat back to a frontwardly tilted posture, so that the operation is liable to become cumbersome. Moreover, the seat provided with the restriction device becomes structurally complicated to cause an increase in cost.